Abstract
The structure of the title compound, [CrCl2(C10H24N4)][Cr(HCONH2)2(C10H24N4)][ZnCl4]2 (C10H24N4 = 1,4,8,11-tetra-aza-cyclo-tetra-decane, cyclam; HCONH2 = formamide, fa), has been determined from synchrotron X-ray data. The asymmetric unit contains two independent halves of the [CrCl2(cyclam)]+ and [Cr(fa)(cyclam)]3+ cations, and one tetra-chlorido-zincate anion. In each complex cation, the CrIII ion is coordinated by the four N atoms of the cyclam ligand in the equatorial plane and two Cl ligands or two O-bonded formamide mol-ecules in a trans axial arrangement, displaying a distorted octa-hedral geometry with crystallographic inversion symmetry. The Cr-N(cyclam) bond lengths are in the range 2.061 (2) to 2.074 (2) Å, while the Cr-Cl and Cr-O(fa) bond distances are 2.3194 (7) and 1.9953 (19) Å, respectively. The macrocyclic cyclam moieties adopt the centrosymmetric trans-III conformation with six- and five-membered chelate rings in chair and gauche conformations. The crystal structure is stabilized by inter-molecular hydrogen bonds involving the NH or CH groups of cyclam and the NH2 group of coordinated formamide as donors, and Cl atoms of the ZnCl4 2- anion as acceptors.
Highlights
The structure of the title compound, [CrCl2(C10H24N4)][Cr(HCONH2)2(C10H24N4)][ZnCl4]2 (C10H24N4 = 1,4,8,11-tetraazacyclotetradecane, cyclam; HCONH2 = formamide, fa), has been determined from synchrotron X-ray data
The CrIII ion is coordinated by the four N atoms of the cyclam ligand in the equatorial plane and two Cl ligands or two O-bonded formamide molecules in a trans axial arrangement, displaying a distorted octahedral geometry with crystallographic inversion symmetry
The crystal structure is stabilized by intermolecular hydrogen bonds involving the NH or CH groups of cyclam and the NH2 group of coordinated formamide as donors, and Cl atoms of the ZnCl42À anion as acceptors
Summary
Each cyclam moiety in the two CrIII complex cations adopts the most stable trans-III conformation. The Cr—N(cyclam) bond lengths are in the range 2.061 (2) to 2.074 (2) A , in good agreement with those observed in trans-[Cr(ONO)2)(cyclam)]BF4 [2.064 (4)–2.073 (4) A ; De Leo et al, 2000], trans-[Cr(NH3)2(cyclam)][ZnCl4]ClÁH2O [2.0501 (15)–2.0615 (15) A ; Moon & Choi, 2016a], trans-. The uncoordinated ZnCl42À counter-anion remains outside the coordination sphere of the two CrIII ions and has a distorted tetrahedral geometry as a result of its involvement in hydrogen-bonding interactions. It exhibits Zn—Cl bond distances in the range 2.2555 (8) to 2.3035 (8) Aand Cl—Zn—Cl angles ranging from 104.84 (4)–
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